The Effect of Different Active Sites on the Catalytic Activity of Fe-ZSM-5 Zeolite for N2O Direct Decomposition

Fe-modified ZSM-5 zeolites (Si/Al = 25) were prepared by adopting the liquid ion-exchange method with nitrate and oxalate of iron as Fe precursors and their catalytic performance was studied in the N₂O decomposition reaction. The results of FT-IR and H₂-TPR investigations indicated that (i) part of the iron ions could replace Brönsted acid protons at the straight channel wall (α sites), intersection of straight and sinusoidal channels (β sites), and sinusoidal channel wall (γ sites) within the ZSM-5 zeolite; and (ii) different Fe precursors gave rise to various distributions of α, β, and γ sites. We observed that the Fe-ZSM-5 catalyst prepared with iron oxalate as Fe precursor outperformed the ones prepared with iron nitrate as Fe precursor in the direct decomposition of N₂O. Furthermore, the catalytic activity of iron ions located at the α sites was higher than those of iron ions located at the β and γ sites.     

Electrochemically induced hydrogenolysis of 1,1-dibromoalkenes to vinyl bromides

Vinyl bromides 2a-f, useful intermediates in organic synthesis, have been obtained under mild conditions and in good yields via electrochemical reduction of 1,1-dibromoalkenes 1a-f (readily available substrates). The reduction has been carried out in MeCN-tetraethylammonium perchlorate (TEAP) solutions, in the presence of a proton donor, at a Au, Hg, C or Ag cathode. The use of specific reducing agents, catalysts and bases, employed in the classical procedures, has been avoided. The isomeric E/Z ratio in vinyl bromides 2a-f is affected by the cathode material.     

Catalytic Activities of Alcohol Transformations Over 8-Ring Zeolites

Aluminosilicate H/CHA and H/MTF zeolites show remarkably different catalytic activities in the methanol and ethanol transformations although they have similar pore size of 8-membered ring structures. Moreover, the produced ethylene is further converted on H/CHA, but H/MTF is not active for the ethylene transformation. The correlations between the distinct catalytic differences and their intrinsic structural properties, including topology and acidity, are discussed.     

Characterization of H-FER and H-TON using temperature-programmed desorption of alkylamines

Simultaneous temperature-programmed desorption (TPD) and thermogravimetric analysis (TGA) measurements were performed with n-propylamine and isopropylamine in H-FER and H-TON in order to test whether the Brønsted-acid sites associated with the 10-ring, straight channels in H-FER could be distinguished from the acid sites in the side cavities. In H-TON, the saturation uptakes were identical for both amines, as were the acid-site densities determined from the amounts of amine which reacted to olefin and ammonia products above 600 K. By contrast, the saturation uptake for isopropylamine in H-FER was much lower than the uptake of n-propylamine and the site density determined from the amounts which react were also significantly lower. It is argued that the n-propylamine results for H-FER provide a measure of the total Brønsted-acid-site density, while the isopropylamine results provide a measure of the site density in the 10-ring channels.     

CH3ONO 与 Br 自由基反应的机理研究

运用量子化学B3LYP方法,在6－311＋＋g（ d,p）基组水平上研究Br自由基和CH3 ONO的反应机理,优化得到了反应途径上反应物、过渡态和产物的几何构型;在B3LYP／6－311＋＋g（ d,p）优化的构型基础上,以CPCM模型得到了其在水溶液中各点的能量。研究结果表明：Br自由基与CH3 ONO有3种反应机制。第1种是Br自由基加成到CH3 ONO分子C原子上消除NO2的机制,第2种是Br自由基加成到CH3 ONO分子甲氧基O原子上消除NO的加成－消除机制,第3种是Br自由基对H直接夺取的机制。     

天然抗氧化剂的筛选

对７００余种中药和香辛料的抗氧化活性进行了大规模的筛选，发现有６４种植物有明显的抗氧化活性，２４种植物的抗氧化活性很强。其中有几种植物的抗氧化活性的筛选和研究，如荔枝草，降真香，紫草，血竭是以前未见报道过的。     

Epoxidation of n-hexene and cyclohexene over titanium-containing catalysts

TS-1, Ti-beta and Ti-MCM-41 molecular sieves have been prepared by direct hydrothermal synthesis method and applied to the epoxidation of n-hexene and cyclohexene with H₂O₂ under mild conditions. Ti-beta with extremely low Al content was synthesized by using a seed method to suppress the formation of diol produced by Brønsted acid sites present in Ti-beta. It was also found that a large amount of by-products (1-ol and 1-one) formed over hydrophilic Ti-MCM-41. We further modified Ti-MCM-41 by silylation with bis(trimethylsilyl) trifluoroacetamide (BSTFA). Among these catalysts, the Ti-beta with low content of Al enhanced the yield of epoxide and suppressed the formation of diol markedly. The silylated Ti-MCM-41 reduced the formation of by-products and promoted the yields of epoxide significantly. Based on experimental results, a reaction mechanism with two parallel and competitive reactions was proposed.     

采用能量色散X荧光仪同时测定Co,Mn,Br元素

建立了用能量色散X荧光仪同时测定Co,Mn,Br 3种共存元素的新方法。优化了操作条件,讨论了影响因素,考察了方法的精密度和准确度。其中Co回收率为95.3％-103.0％,Mn回收率为96.0％-104.0%,Br回收率为94.8％-105.0％。用于精对苯二甲酸化工装置试样中Co,Mn,Br的同时测定,结果满意。     

含水层有效孔隙度的实验研究

该文通过对两组土样分别采用溴离子 (Br-)、3 H作示踪剂的示踪渗透实验 ,测定了土样的有效孔隙度 ,分析了实验结果的可靠性 ,认为引起两组实验结果之间差异的原因 ,可能是由于实验土样是带负电荷的黄土颗粒 ,它对溴离子 (Br-)有排斥作用 ,而3 H不受这一作用的影响 ,因此溴离子 (Br-)在相同介质和水头差的作用下运动得比3 H略快     

钙-5-Br-PADAP-Triton X-100显色反应的研究和应用

在 pH8 0～ 10 0范围内 ,有非离子表面活性剂TritonX 10 0存在下 ,钙与 5 Br PADAP生成 1∶1稳定的有色络合物 ,其最大吸收波长λmax=5 5 5nm ,ε =3 6 7× 10 4,钙量在 0～ 2 0 μg/2 5mL范围内符合比尔定律 方法灵敏 ,准确 ,快速 ,可用于测定球墨铸铁、合金钢中的微量钙